Hitherto, a carbon material, such as graphite, carbon nanotubes or carbon particles, has been widely used as an adsorbent, a wiring material, or a reinforcing agent or filler into a resin. In recent years, attention has been paid to exfoliated graphite, which is obtained by peeling off flakes from graphite and has a smaller number of graphene layers laminated than graphite.
When a carbon material as described above is used, the material is dispersed in a solvent or synthetic resin in many cases. However, exfoliated graphite, carbon nanotubes or the like is large in aspect ratio to cause a problem of being low in dispersibility therein. Patent Document 1 listed below discloses a modified carbon material in which a carbon material having a graphene sheet structure is heightened in dispersibility. Patent Document 1 discloses a modified carbon material obtained by adding a fragment obtained by radical-decomposing an azo-type radical polymerization initiator containing a carboxyl group to a carbon material having a graphene sheet structure, for example, vapor phase growth carbon fibers or carbon nanotubes. This modified carbon material has been made high in dispersibility in water by the modification with the carboxyl group.